The publication WO/1986/004306 presents the solution of the hydrostatic driving system of a slip-steered vehicle having a pair of hydraulic motors on each side of the vehicle, each of the hydraulic motors comprising two controllable hydraulic pumps, which are preferably mounted on the same driven shaft. Each of the hydraulic motors is arranged to drive at least one wheel. The invention is characterized in that the two hydraulic pumps are connected to the corresponding pairs of hydraulic motors via a closed system of pipes and valves, where the closed system permits switching the hydraulic motors from being connected in parallel to being connected in series.
The publication WO/1996/000865 presents the solution of an automatic, Inertial, Continuously Variable, Hydrostatic Transmission (C.V.T.) for motor vehicles, comprising a pair of reversible vane pump/motor (A, B) units connected in a closed circuit. The vane pump/motor (A, B) units are of the new “moving side” type with fixed eccentricity. The driving pump/motor unit (A) is driven by the engine and via a torque-sensitive inertial connection, which has a screw, a nut and a pressure spring, moves through the hydrostatic fluid to transfer the motion to the motor/pump (B) of the wheel. An alternative embodiment lacks the torque-sensitive connection, and the transmission ratio is varied continuously, but it is done manually without the use of a clutch.
The publication WO/1998/049470 presents a multi-range, synchronous shifting, hydromechanical transmission for application in an automotive drivetrain. The transmission receives split power inputs from the engine; one input being geared down to a lower speed for driving a continuously variable hydrostatic transmission unit, while the other input drives a counter shaft from which mechanical outputs are taken at different speed ratios. A planetary gear set, driven by the hydrostatic transmission unit, is shiftable to provide either a low continuously variable speed hydrostatic output, which is suitable for transmission operation in low output ranges, or a high continuously variable speed hydrostatic output, which is suitable for transmission operation in high output ranges. A gear system includes a plurality of gearsets selectively controlled by clutches and brakes to combine the hydrostatic and the mechanical outputs to produce four continuously variable forward ranges and one continuously variable reverse range.
The present invention resulted from the recognition that there is a need for a gear box that is easily adaptable to a hybrid solution for torque transmission fur use in a brushless electric motor. Such a gear box should have high efficiency as compared with the efficiency of gear boxes based on the gear wheel system and should have a simple construction with relatively small dimensions. Additionally, the gear box should not be sensitive to overloading and capable of protecting the drive system from damage.